The present invention relates to an end mill and a method of manufacturing the same. More specifically, the present invention relates to an end mill which is attached to a spindle of a milling apparatus or the like to be used in the case where a workpiece is machined to form a fine groove, and relates to a method of manufacturing the same.
In optoelectronics devices, optical components, such as diffraction gratings and microlens arrays, which have fine structures, are used. In this kind of components, forming finer structures is demanded according to technical trends such as the reduction of wavelengths of light sources and the miniaturization of devices. Moreover, the commercialization of optical integrated circuits in which optical waveguides formed on a substrate are combined is in progress.
On the other hand, in medical and biochemical fields and the like, instruments having structures for dealing with very small amounts of samples are also used. Such instruments include biochips, microneedle arrays, and chemical micro reactors. In this kind of instruments, too, fine structures are demanded which have higher accuracy and smoother finished quality.
The entire sizes of products having such a fine structure are approximately several mm to several tens of mm. On the other hand, for the form accuracy and the surface roughness of the structure, accuracy of a submicron order to approximately several tens of μm is demanded. As a method of processing a fine shape on the order of microns, lithography technology is known in which semiconductor manufacturing technology is applied. It should be noted, however, that since molding methods in this kind of technology utilize chemical reactions, the controllability of a processing depth and that of the molding of details such as an edge are low.
Moreover, in chemical processing methods, the number of steps for completing a product is large, and each step takes a certain period of time. In addition, since a particular chemical reaction is utilized, there are restrictions on a material as an object of processing. Accordingly, it is difficult to mold, for example, lithium niobate which is a material for an optical waveguide, a germanium lens used in an infrared optical system, or the like by a chemical processing method.
Other than the above-described chemical processing methods, Japanese Patent Laid-open Official Gazette No. 2002-283174 (Patent Document 1) discloses a high-accuracy machine tool which can perform fine machining. This makes it possible to control the position of a processing tool with accuracy on the order of microns. Moreover, Japanese Patent Laid-open Official Gazette No. 2004-148471 (Patent Document 2) discloses the structure of an end mill which can be attached to the above-described machine tool to perform micromachining. This makes it possible to form a fine structure using a tool having a diamond tip. Furthermore, Japanese Patent Laid-open Official Gazette No. 2004-345031 (Patent Document 3) discloses an end mill for micromachining which has other structure. This makes it possible to form a fine structure even in a high-hardness material such as metal.
However, since an object to be machined by the end mill described in Patent Document 2 is a resin material, the bending strength of a cutting edge portion of the end mill is low. Accordingly, there is a problem that breakage easily occurs if a metal material which is formed into, for example, a die is machined using this end mill.
Moreover, on the end mill described in Patent Document 3, there is a structural restriction that the crystalline orientation thereof is specified. For example, in the case where a groove is formed in a workpiece, it is easy to form a groove having a V-shaped cross section in which the opening side is wider, but, on the other hand, it is difficult to form a machined surface parallel to the rotation axis of the end mill.